Likely the one measure you already have in place, anti-malware and host-based intrusion prevention systems (HIPS) are a critical piece of the security puzzle, which includes policies and standards, employee awareness, network intrusion defense and access control, segmentation and system access control.
Access control is one of the foundational elements of a security system. Making sure that your network is as secure as possible means making sure that only users who need access to your system, have access, and that that access is restricted to the most limited degree possible.
Part of being strategic and proactive about your security stance involves network segmentation. Limiting and partitioning network access according to your security and performance requirements ensures that traffic can be more effectively controlled and monitored as it moves between security zones.